14,2 :misc. publication 273 u. s. dept. of agriculture 



KEY TO DIAGNOSIS OF INSECT INJURY TO WOOD AND WOOD 



PRODUCTS 



A. Insects attacking green, unseasoned, or seasoning wood, living or dying 



trees, or freshly felled trees or logs, and projecting their tunnels 

 directly into and through the wood. 



1. Small, circular, open pinholes, often surrounded by dark 



stains ; diameter uniform and less than one-eighth 

 inch : made by small, brown, shining, cylindrical 

 beetles ambrosia beetles, page 143. 



2. Large, more or less circular holes in wood ; diameter more than 



one-eighth inch ; lightly filled with pellets ; wood stained 

 or not. 



a. Nearly circular holes of medium size in wood of broad- 

 leaved trees made by caterpillers 



clear-wing moths, page 139. 

 &. Very large irregular holes one-half to 1 inch in 

 diameter in broadleaved trees, usually lined with 

 a silky yellowish-brown web carpenter moths, page 154. 



3. Circular, oval, or irregularly shaped tunnels of varying width 



gradually increasing to more than one-eighth inch in size ; 

 usually tightly packed with fine boring dust or coarse 

 frass, except at ends occupied by larvae or pupae. 



a. Tunnels flatly oval, usually lightly packed with arc- 



like layers of sawdust-like borings and pellets of 

 woody excrement, and surface of wood marked by 

 fine, transverse, crescentric lines ; made by 

 slender, white, legless grubs shaped like horseshoe 

 nails with very wide, flat segments back of head ; 

 first segment with a well developed plate on both 

 upper and lower surfaces, upper plate marked 

 with a central line, groove, V or Y 



flatheaded borers, page 147. 



b. Tunnels broadly oval to nearly circular, tightly packed 



with sawdustlike borings and pellets of wood ex- 

 crement ; made by long, thick, white, apparently 

 legless grubs, with horny plate on top of first 

 thoracic segment, which is somewhat enlarged 



roundheaded borers, page 150. 



c. Perfectly circular holes in wood, not evident in cam- 



bium, made by long, white, cylindrical grubs with 

 small heads, fleshy lobes for thoracic legs, and 

 the abdomen terminating rearwards with a sharp 

 horny prong-- horntails and certain Coleoptera, page 155. 



B. Insects attacking living trees and causing black checks, pitch pockets, 



pitch flecks, gum spots, or ring distortion, but not causing pinholes 

 or wormholes. 



1. Black checks showing in wood of conifers, surrounded by 



curled or distorted wood bark maggots, page 158. 



2. Birdseye pitch flecks in pine pitch midges, page 54. 



3. Double rings, distorted rings, retarded growth ^_ defoliators, page 58. 



4. Pitch pockets, gum spots, and pitch streaks in coniferous 



woods bark beetles, page 96. 



„ flatheaded borers, page 132. 



pitch moths, page 139. 



terminal-feeding insects, page 29. 



C. Insects attacking sawed lumber, seasoned wood, or utilized wood 



products. 



1. Small wormholes in wood, tightly packed with a very fine 

 powder, powder sometimes pushed out through holes in 

 wood. Usually working in very dry wood. 



a. Small, nearly round tunnels in various hardwoods 



powder-post beetles, page 159. 

 6. Irregularly shaped tunnels in softwoods and hard- 

 woods (see above under A, 3). 



■^Also from causes other than insects. 



